At STR, the pressure of a gas is _____ torr its temperature is ________ degree C

Question

At STR, the pressure of a gas is _____ torr its temperature is ________ degree C = _____ K. The molar volume of a gas at STP is ____ ml., If the initial conditions of a gaseous system are: P_1, V_1, T_1, and its final conditions are P_2, V_2, T_2, the final volume (V_2) of the gas expressed in terms of V_1, P_1, T_1, P_2, and T_2, is When hydrogen gas is collected by displacement of water, there is always water vapor mixed with the gaseous hydrogen. The partial pressure exerted by water vapor is called its vapor pressure and its numerical value depends on the ______ of the gaseous mixture Look up the vapor pressure of water vapor at 20 degree C in Appendix G. Its vapor pressure is _____ torr If the pressure of a gas is 760 mm of water, its pressure is ___ torr (mm of mercury). (the density of mercury is 13.6 g/mL). The equivalent weight of a metal is that weight of the metal that will liberate 1.008 g of hydrogen gas (H_2) from an acid. However, 1.008 g of hydrogen is _____ mol = ______ mL at STP The equivalent weight of aluminum is 9.0 g. The number of mols of hydrogen gas produced by the reaction between 2.00 g of Al and an acid is ______ mol. The volume of the liberated gas at STP is _____ ml

Explanation / Answer

1.STP refer to standard conditions of temperature and pressure. At STP, the pressure is 1 atm and temperature is 0deg.c. Expressed in terms of Torr, the pressure will be 760 Torr and temperature is 0 deg.c= 273K

2. At STP ( 1atm pressure and 273K), PV= nRT, V/n= RT/P= 0.0821 L.atm/mole.K*273K/1 atm= 22.4L/mole= 22.4*1000ml/mole= 2.24*104 ml/ mole

3. Gas law equation at two different conditions of temperature and pressure can be written as

P1V1/T1= P2V2/T2 ( when moles remain constant)

V2= P1V1T2/(P2T1)

4. when hydrogen is collected by displacement of water, the total pressure= partial pressure of hydrogen+ saturated vapor pressure of water. Vapor pressure is a function of temperature. Hence the numerical value of vapor pressure depends on the temperature of the gas mixture.

5. Antoine equation for water can be used to calculate the vapor pressure of water at 20 deg.c

The equation is logpsat(mm Hg)= 8.07131-1730.63/(t+233.426), where t is in deg.c

Hence at 20 deg.c, log Psat(mm Hg)= 8.07131-1730.63/(20+233.426) , Psat= 17.47 mm Hg= 17.47 Torr

6. Given pressure of gas is 760mm Water

Pressure= density of water* g* mm of water = density of mercury* g* mm of mercury

760*9.8*1= 13.6* 9.8*h, h= mm of mercury

Hence h= 55.88 mm of mercury

7. 1.008 gm is mass of 1 mole of hydrogen and at STP, 1 mole of any substance occupies 22.4 L=22.4*1000ml

8. moles of Hydrogen produced= mass/equivalent weight= 2/9 moles

1 mole of any substance occupies 22.4 L

2/9 moles of hydrogen occupies (2/9)*22.4 L =4.97 L

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